At present it is still commonplace for waste water produced on ships to be passed untreated into the sea. It is however also already known to subject waste water to a biological clarification process. A disadvantage in this case is that it is difficult to adapt it to the amount of waste water being produced, as waste water from ships is typically composed of different waste water streams which as a rule have widely fluctuating compounds. Furthermore, there is an insufficient breakdown of nitrates in such clarification processes. As a result, the clarified water is passed into the sea water with unacceptable levels of nitrates and nitrites.
A compact biological water clarification assembly is known from DE 197 49 699 A1. The assembly for treating waste water comprises a primary clarification stage, a biological clarification stage and a final clarification stage in a single container. The primary clarification tank itself consists of three tanks. Water enters the first tank from where the waste water is passed into a further primary clarification tank located below the first tank, from where the waste water is passed into the third primary clarification tank which is located in the vicinity of the second primary clarification tank. In the third primary clarification tank a rotating body is arranged with which, in this tank, part of the aerobic biological purification of the waste water is carried out.
A device is known from DE 31 45 797 A1 for biological waste water purification where, for the purification process, the waste water is fed in with vacuum suction by means of a liquid jet pump which is driven by a circulating water pump. A buffer tank into which the waste water first enters and which is connected to the suction side of the liquid jet pump is arranged in such a way that there is a vacuum cushion in the buffer tank. In this manner multiple use of toilets and/or waste water collection points are/is achieved and at the same time efficient aerobic breakdown of the contaminants is ensured.
A transportable compact clarification assembly is known from DE 295 17 891 U1, which is built into a welded structural steel container. It contains a two-stage bioreactor. The bioreactor working in the aeration process is connected via an intermediate clarification stage to a low load reactor containing a forced-aeration fixed bed cascade. The excess sludge is fed out of the post-clarification tank into a high load tank, which is connected in series to the bioreactor. The excess sludge from the intermediate sludge circuit between the intermediate clarification stage and the high load tank is discharged into an aerated sludge stabilization tank/sludge collector.
In DE 42 07 077 C2 a compact clarification assembly with a sludge recirculation element is disclosed. A rectangular tank is divided up into a pre-clarification tank, an aeration tank with an immersed aerator and a post-clarification tank. At least one liquid overflow device is provided between the aeration tank and the post-clarification tank. On the bottom of the aeration tank at a distance from the horizontal recirculation slot, guide elements are offset obliquely from one another and spaced apart along the width of the tank. At the lower end of the partition wall between the aeration tank and the post-clarification tank above the slot is a guide element, extending horizontally along the width of the tank and arranged obliquely downwards into the aeration tank.
A process and an assembly for the biological purification of waste water by targeted denitrification is known from DE 42 21 867 C2. The activated sludge withdrawn as excess sludge is disintegrated by a mechanical cell wall disintegration process into a disintegrated product and thus processed to an internally available source of hydrocarbon and metered specifically for denitrification. All the organic carbon of the waste water which can be biologically broken down is converted into the gas phase by continuous recirculation.
From EP 0 501 355 A1 a process is known for the anaerobic treatment of water, in particular for the microbial degradation of nitrates from drinking water. The raw water to be treated is passed via two fluidised bed reactors connected in series and in the operating state is transported with support material overgrown by biomass from a respective reactor stage into the following reactor stage. The support material is passed with the water stream leaving the last reactor into a separation unit from where the separated support material is recirculated into the first reactor stage. Depending on the pressure drop in the individual reactor stages the water to be treated can be passed via reactor stages staggered in height.